Here's why:
* Pronunciation: The rule is based on how the "ch" sound is pronounced. If "ch" makes a soft /ch/ sound like in "church" or "bench," we add "es" to make it plural (e.g., churches, benches).
* Consistency: This rule helps maintain consistency in spelling and pronunciation. Imagine if "church" became "churchs" - it would sound awkward and be confusing to read.
However, if the "ch" makes a hard /k/ sound, we add "s" instead:
* Examples: stomach -> stomachs, epoch -> epochs, monarch -> monarchs
The bottom line: It's not about the letter "ch" itself, but about the sound it makes. Remember, there are always exceptions to rules in English!